NEW YORK – The president of the leading Southern Baptist seminary has incurred sharp attacks from both the left and right by suggesting that a biological basis for homosexuality may be proven, and that prenatal treatment to reverse gay orientation would be biblically justified.

The Rev. R. Albert Mohler Jr., one of the country's pre-eminent evangelical leaders, acknowledged that he irked many fellow conservatives with an article earlier this month saying scientific research "points to some level of biological causation" for homosexuality.

Proof of a biological basis would challenge the belief of many conservative Christians that homosexuality — which they view as sinful — is a matter of choice that can be overcome through prayer and counseling.

However, Mohler, president of the Southern Baptist Theological Seminary in Louisville, Ky., was assailed even more harshly by gay-rights supporters. They were upset by his assertion that homosexuality would remain a sin even if it were biologically based, and by his support for possible medical treatment that could switch an unborn gay baby's sexual orientation to heterosexual.

"He's willing to play God," said Harry Knox, a spokesman on religious issues for the Human Rights Campaign, a national gay-rights group. "He's more than willing to let homophobia take over and be the determinant of how he responds to this issue, in spite of everything else he believes about not tinkering with the unborn."

Mohler said he was aware of the invective being directed at him on gay-rights blogs, where some participants have likened him toJosef Mengele, the Nazi doctor notorious for death-camp experimentation.

"I wonder if people actually read what I wrote," Mohler said in a telephone interview. "But I wrote the article intending to start a conversation, and I think I've been successful at that."

The article, published March 2 on Mohler's personal Web site, carried a long but intriguing title: "Is Your Baby Gay? What If You Could Know? What If You Could Do Something About It?"

Mohler began by summarizing some recent research into sexual orientation, and advising his Christian readership that they should brace for the possibility that a biological basis for homosexuality may be proven.

Mohler wrote that such proof would not alter the Bible's condemnation of homosexuality, but said the discovery would be "of great pastoral significance, allowing for a greater understanding of why certain persons struggle with these particular sexual temptations."

He also referred to a recent article in the pop-culture magazine Radar, which explored the possibility that sexual orientation could be detected in unborn babies and raised the question of whether parents — even liberals who support gay rights — might be open to trying future prenatal techniques that would reverse homosexuality.

Mohler said he would strongly oppose any move to encourage abortion or genetic manipulation of fetuses on grounds of sexual orientation, but he would endorse prenatal hormonal treatment — if such a technology were developed — to reverse homosexuality. He said this would no different, in moral terms, to using technology that would restore vision to a blind fetus.

"I realize this sounds very offensive to homosexuals, but it's the only way a Christian can look at it," Mohler said. "We should have no more problem with that than treating any medical problem."

Mohler's argument was endorsed by a prominent Roman Catholic thinker, the Rev. Joseph Fessio, provost of Ave Maria University in Naples, Fla., and editor of Ignatius Press, Pope Benedict XVI's U.S. publisher.

"Same-sex activity is considered disordered," Fessio said. "If there are ways of detecting diseases or disorders of children in the womb, and a way of treating them that respected the dignity of the child and mother, it would be a wonderful advancement of science."

Such logic dismayed Jennifer Chrisler of Family Pride, a group that supports gay and lesbian families.

"What bothers me is the hypocrisy," she said. "In one breath, they say the sanctity of an unborn life is unconditional, and in the next breath, it's OK to perform medical treatments on them because of their own moral convictions, not because there's anything wrong with the child."

Paul Myers, a biology professor at the University of Minnesota-Morris, wrote a detailed critique of Mohler's column, contending that there could be many genes contributing to sexual orientation and that medical attempts to alter it could be risky.

"If there are such genes, they will also contribute to other aspects of social and sexual interactions," Myers wrote. "Disentangling the nuances of preference from the whole damn problem of loving people might well be impossible."

Not all reaction to Mohler's article has been negative.

Dr. Jack Drescher, a New York City psychiatrist critical of those who consider homosexuality a disorder, commended Mohler's openness to the prospect that it is biologically based.

"This represents a major shift," Drescher said. "This is a man who actually has an open mind, who is struggling to reconcile his religious beliefs with facts that contradict it."